Controlling ECL loop macro using results of a query

Question

We are trying to write a loop macro with a break function. Basically we would like to repeat a certain action until X (derived from a Dataset) is true. The compiler doesn't seem to like this approach however (returns 'Constant expression expected') so we were wondering if there is a known workaround?

An entirely artificial example is provided below, called by:

LoopFunction(5);  

from a BWR window.

EXPORT LoopFunction(NMax = 5) := MACRO

  Rec := RECORD
    INTEGER i;
  END;

    #DECLARE(i);


  OUTPUT(DATASET([1], REC), ,'~TEMP::MB::LOOPTEST' + %i%, COMPRESSED, OVERWRITE);

    #SET(i, 2);

  shouldIbreak :=  DATASET('~TEMP::MB::LOOPTEST' + (%i% - 1), Rec, THOR);

  #LOOP

    OUTPUT(shouldIbreak +DATASET([%i%], REC), ,'~TEMP::MB::LOOPTEST' + %i%, COMPRESSED, OVERWRITE);

    #SET (i, %i%+1);    

        #IF (COUNT(shouldIbreak) > Nmax);
       #BREAK
        #END
    #END

ENDMACRO;

Answer 1

This is possible using the LOOP() command, you may specify a break condition there. See the (mediocre) documentation here and a blog post here